A video reproduction of an image, which here is intended to include a two-dimensional picture or an actual three-dimensional object, is typically made by optoelectrically scanning the object with an image orthicon or a more modern charge-coupled device to produce a succession of rows of picture-element signals. Each of these signals contains data in analog form about the brightness of light (the luminance signal) at a respective spot on the image and about the color of the respective spot (the chrominance signal).
Typically these analog signals are recorded as is, or are transferred as is to other devices capable of reforming the image. Such other peripheral device could be a graphics-capable printer, a video monitor, or even a copier device using electrically inscribable paper.
Clearly whenever analog information is used noise becomes a problem. This is particularly true in video imaging where vast amounts of relatively sensitive analog information must be acted on electronically without adding distortion and noise. The slightest disturbance in a single one of the picture-element signals, and there are upward of 200.multidot.10.sup.3 such signals for a reasonably detailed picture, results in an obvious flaw in the resultant reproduction.
Another problem with the prior-art systems is that they work very poorly in low-light conditions, particularly when applied to printing an image. Under such conditions it is usual for the noise, which effectively makes the picture fuzzier, to be even greater, as the amplitude of the random noise signals remains the same while that of the analog picture signal decreases.